CA2770627C - Process for upgrading a pyrolysis oil, in particular in a refinery - Google Patents

Abstract

The invention relates to a process for upgrading a pyrolysis oil comprising the following steps: - hydrodeoxygenation treatment (10) of the pyrolysis oil (12) and separation of the effluent (16) obtained into a light aqueous fraction (18) and a heavy organic fraction (20), or separation of the pyrolysis oil into an aqueous fraction and a lignin-rich fraction, - pre-reforming (22) of said aqueous fraction (18) and treatment of the effluent (26) obtained in an SMR unit (28) in order to produce hydrogen (34), - hydrotreatment (40) and/or catalytic cracking and/or visbreaking of said heavy organic fraction (20).

Description

PROCESS FOR THE VALORISATION OF PYROLYSIS OIL, NOTABLY IN REFINERY

The invention relates to a method of upgrading the oil of pyrolysis, especially in refineries.
Pyrolysis oils, or bio-oils, come from the pyroliquefaction, also called rapid pyrolysis at low temperature, wood-type biomass (hardwood, softwood), straw and forest or agricultural biomass residues such as bark, chips, sawdust, bagasse ...
These oils are produced by depolymerization and fragmentation components of biomass (holocellulose (cellulose, hemicellulose), lignin) under the influence of a rapid increase (<2 seconds) of the temperature at 450 C-550 C and rapid quenching of intermediate products of degradation.

They can be considered as microemulsions in which the liquid continuous phase is an aqueous solution of decomposition products of cellulose and hemicellulose and of small lignin molecules. The continuous liquid phase stabilizes the organic discontinuous phase consisting essentially of macromolecules of pyrolytic lignin.
They consist of water and a complex mixture of oxygenated compounds. Their elemental composition is close to the composition of the starting biomass with in particular a important in oxygen.
The analysable mean organic molecular composition can to be described by the families presented in Table 1.

Table 1 Content (% m / m) Pyrolytic lignin 15-25 Organic acids 5-15 Aldehydes and hydroxy-aldehydes 5-20 Ketones and hydroxy ketones 0-15 Phenols 15-35 Methanol, Ethanol 1-5

2 Table 2 below groups the main characteristics pyrolysis oils.

Table 2 Properties Pyrolysis oils pH 2.0-3.7 Water content (% m / m) 15-35 Density at 15 C

(Kg / m3) Viscosity at 20 C (mm2 / s) 50-130 Viscosity at 40 C (mm2 / s) 12-35 Elemental analysis C 30-50 (% m / m) H 6-9 Solids () 0.01-2 Ash (% m / m) 0.01-0.20 Higher Calorific Value PCS (MJ / kg) Metals (K + Na) (mg / kg) 10-300 Pyrolysis oils are characterized by a density high and a variable viscosity depending, inter alia, on the starting biomass. As they are acidic and therefore corrosive, their use requires the use of specific materials that are resistant to corrosion, such as stainless steel, high density polyethylene, propylene ...
On the other hand, pyrolysis oils are chemically unstable and thermally. The chemical instability of pyrolysis oils is reflected in the evolution over time of their physical properties.
chemicals (viscosity, water content, solids content, etc.) result in a two-phase separation. The thermal instability of pyrolysis oils translates into a very rapid evolution of their properties when heated to temperatures above C. Because of this instability, these products can not be valued in the refinery in their raw form, except in an application for

3 combustion with some modifications of the installations current. For any other refinery application, it seems necessary to stabilize the pyrolysis oils before use, by example by eliminating or transforming the most reactive.
Pyrolysis oils have an average water content of 25% w / w, an oxygen content of the organic fraction of the order of 35-40% w / w and a molecular structure of great complexity.
Their water content can also lead to partial separation phase affecting their other physical properties.
Finally, their ash and alkaline contents can lead to deposit formation and fouling of facilities.
Moreover, because of their hydrophilic nature and their polarity, fast pyrolysis oils are not miscible with hydrocarbons. Thus, pyrolysis oils can not be valued as such in a refinery mixed with cuts hydrocarbons of fossil origin.
Thus, because of their particular properties, the use of Pyrolysis oils raise many problems.
Currently, the main valuation routes studied are the combustion of pyrolysis oil in boilers or turbines gas for producing heat and / or electricity, or production of bases for chemistry.
To be used in refineries for production of fuel, the pyrolysis oils must undergo a pretreatment to stabilize them. Such pretreatment can be a deoxygenation step that can be:
- total, to transform bio-oils into fuel bases, - partial (> 90%), to make the oils miscible with the hydrocarbon cuts of petroleum origin and thus introduce it into the refining scheme, - partial (> 50%), to stabilize the oils with a view to subsequent use.
This deoxygenation can in particular be carried out by hydrodeoxygenation (HDO), following the simplified reaction:
C6H804 + 4H2 - C6H8 + 4H2O

4 However, the amount of hydrogen required is high (from 2 to 7 % by weight by mass of pyrolysis oil) and has a significant impact the cost of treating these pyrolysis oils (about 1/3 of the cost price of the fuel bases produced) and on the analysis of the Life Cycle Assessment (LCA) which is a tool for assessing impacts on the environment of a system, here the biofuel, including the whole activities from the extraction of raw materials to the end-of-waste management. So, as far as the biofuel produced from the pyrolysis oil, it is estimated that 2/3 total fossil emissions are due to the production of hydrogen necessary for the hydrodeoxygenation of the pyrolysis oil. Now, a too much hydrogen consumption during HDO can be unacceptable to consider the fuel bases produced as biofuel according to the sustainability criteria established by the European Directives, such as Directive 2009/28 / EC, which specifies that from 2013, the reduction of greenhouse gas emissions resulting from the use of biofuels must be at least 35%
compared to fossil fuels. This reduction must be from 50% from 2017. There is therefore a great need to reduce the impact of hydrogen consumption during the treatment of oils pyrolysis for the production of fuel.

One solution could be to use the oils of pyrolysis themselves to produce hydrogen, for example by catalytic steam reforming.
Studies have shown that catalytic steam reforming of oil or fractions of pyrolysis oil conducted under conditions operating conditions close to those used to produce hydrogen at from methane, leads to coke formation, resulting in rapid deactivation of the catalyst.
In particular, fixed bed steam reforming has been studied (Czernik S, French R, Feik C, Chornet E. Hydrogen by catalytic steam reforming of liquid by-products from biomass thermoconversion processes. Ind Eng Chem Res. 2002 (41) 4209-4215) on a so-called aqueous fraction of pyrolysis oils. Said fraction was obtained by adding water to force a phase separation with the lignin fraction pyrolytic. The deposit of coke, however, causes a deactivation fast catalyst limiting the time of the test to a duration (4 hours) less than the time required for the regeneration of the catalyst (6 to 8 hours), highlighting the limitations of the fixed bed for this type of reactions. These phenomena are even more marked by using

5 the total oil as steam reforming charge: in the same operating conditions, the maximum duration of a test reaches 45 minutes while the catalyst regeneration time is 8 hours.
As a result of this work, fluidized bed tests were carried out by the same authors. The disadvantage of the fluidized bed is that of having to use catalysts resistant to attrition phenomena. The performance of the usual catalysts are insufficient and research must be conducted on this subject.
With the same operating conditions as in fixed bed (850 C, S / C
> 5, GC 1 HSV from 800 to 1000 h-1) and the same charge (fraction aqueous solution obtained by phase separation after adding water to the oil pyrolysis), the continuous test duration is more than 100 hours.
It thus appears that the steam reforming of the aqueous fraction of pyrolysis oil is technically feasible in a fluidized bed and reduces the formation of coke. However, attrition catalysts generated by fluidized bed operation requires the development of new catalysts and reactors dedicated to this type of treatment. In addition, the organic fraction of the pyrolysis oil is not recoverable in steam reforming because it contains compounds too heavy for this type of reaction and requires another pretreatment to be valorizable in refinery because this fraction is not miscible with hydrocarbons.
The production of hydrogen from pyrolysis oil by a The process of steam reforming is therefore only conceivable on the fraction water and does not allow a valuation of the totality of the oil. Said aqueous fraction may still contain compounds coke precursors according to the type of separation used to fractionate the oil, the reaction of steam reforming remains difficult to put implemented.
The aim of the invention is to overcome these drawbacks by proposing a method of upgrading pyrolysis oils making it possible to produce hydrogen by valorizing all the treated pyrolysis oils.

WO 2011/02096

6 PCT / FR2010 / 051682 For this purpose, the subject of the invention relates to a method of pyrolysis oil recovery including the following steps = pre-reforming of the light aqueous fraction, resulting from the separation of the pyrolysis oil into a fraction aqueous and a fraction rich in lignin, is obtained after a hydrodeoxygenation treatment of the pyrolysis oil and then separation of the effluent obtained into a fraction light aqueous and a heavy organic fraction, = treatment of said pre-reformed aqueous fraction in a SMR unit to produce hydrogen;

= hydrotreatment and / or catalytic cracking and / or visbreaking said lignin-rich fraction or the fraction heavy organic.

The invention relates more particularly to a method of pyrolysis oil recovery comprising the following steps:
- hydrodeoxygenation treatment of the pyrolysis oil and separation of the effluent obtained into a light aqueous fraction and a heavy organic fraction, pre-reforming of said light aqueous fraction and treatment the effluent obtained in a SMR unit to produce hydrogen, - hydrotreatment and / or catalytic cracking and / or visbreaking of said heavy organic fraction.
The totality of the pyrolysis oil is thus valorized, allowing the production of hydrogen and gasoline bases of the LPG type (Gaz de liquefied petroleum), gasoline, kerosene, diesel, vacuum gas oil ...
The possible hydrodeoxygenation (so-called HDO) of the oil of pyrolysis and then the pre-reforming of the aqueous fraction obtained to produce hydrogen. The problems of coking observed during a direct steam reforming the pyrolysis oil or the aqueous fraction pyrolysis oil are thus removed. Indeed, the implementation of the process according to the invention, and in particular the process of which the first step is a hydrodeoxygenation treatment of pyrolysis oil, leads to the formation of a so-called aqueous phase whose

7 composition is such that the subsequent pre-reforming stage does not lead not to the formation of coke. The composition of this aqueous phase is therefore totally different from the aqueous phase mentioned above, in the state of the art, and obtained by phase separation after adding water to the pyrolysis oil.
The aqueous phase obtained after HDO of the pyrolysis oil usually contains less heavy products and sulfur (poison steam reforming catalysts eliminated in the form of H2S during HDO), that the aqueous fraction obtained by phase separation after adding water to the pyrolysis oil.
Pre-reforming will make it possible to transform the compounds into C2 + in CH4, CO, CO2 and H2 in the presence of a conventional catalyst pre-reforming process, in particular a conventional catalyst for pre-reforming reformer of LPG / naphtha, for example of the Ni or NiO type. This The reaction can for example be carried out in a conventional fixed bed.
The effluent leaving the pre-reformer is then sent to a conventional SMR unit (Steam Methane Reforming which means reforming methane with steam) by adding water vapor to produce H2. This reaction is usually carried out within numerous catalyst-filled tubes arranged in an oven.
Simplified reactions occurring in the pre-reformer can be schematized by the following equations CXHyO2 + (x2) H2O H (x + y / 2-z) H2 + xCO (1) CO + 3H2H CH4 + H2O (2) CO + H2O H CO2 + H2 (3) Balance sheet:
CXHyO2 + (xy / 4-z / 2) H2O H (x / 2 + y / 8-z / 4) CH4 + (x / 2-y / 8 + z / 4) CO2 (4) The reaction occurring at the level of the SMR can be schematized by the following equation:
CH4 + H2OH CO + 3H2.
Advantageously, the hydrogen produced from the fraction light aqueous can be used for hydrodeoxygenation of oil pyrolysis and / or for the hydrotreatment of the organic fraction heavy.
The external supply of hydrogen necessary for the reactions hydrodeoxygenation (HDO) or hydrotreatment (HDT) is thus

8 considerably reduced, and can possibly be deleted in running of the installation according to the composition and amount of aqueous fraction.
For example, with a light aqueous fraction containing 50%
of water and 50% of organic compounds, the amount of H2 produced to cover the H2 requirements of the HDO of the pyrolysis oil. A
external input of H2 is then only necessary at the start of installation, before the start of H2 production.
The effluent obtained during the hydrotreatment of the fraction heavy organic can also be separated into an aqueous fraction light and a heavy organic fraction when the amount of water is important enough to be separated, this light aqueous fraction is then sent to the pre-reforming with the light aqueous fraction resulting from the hydrodeoxygenation of the pyrolysis.
The production of hydrogen can then be increased.
The heavy organic phase from the first HDO can require another hydrotreatment (eg HDO) in order to produce fuel bases.
Moreover, as unlike an organic phase obtained by separation by adding water in pyrolysis oil, this organic phase is miscible with hydrocarbons, it can so be advantageously co-treated with a fossil charge.
Preferably, the organic phase resulting from the HDO of the oil Pyrolysis will account for up to 30% by mass of the unit charge hydrotreating. Advantageously, the co-treatment with the load of fossil origin will occur after a fractionation of the effluent phase organic output of the unit of hydrodeoxygenation of the oil of pyrolysis.
For example, after fractionation, the diesel type cut out of the HDO of the pyrolysis oil can be co-processed in a unit conventional hydrotreating with a diesel type charge of fossil origin. The fossil fuel type fuel can be from the atmospheric distillation of crude oil (Gasoil straight run), vacuum distillation of the atmospheric residue (vacuum gas oil) or a diesel fuel charge resulting from a conversion process. The

9 being able to use an existing unit for the second Hydrotreatment can significantly reduce costs.
Likewise, after splitting, the kerosene type cut or gasoline from the HDO of the pyrolysis oil can be, if necessary, co-processed in a conventional hydrotreating unit with a Kerosene type charge or fossil fuel.

Advantageously, the light aqueous phase resulting from the hydrodeoxygenation of the pyrolysis oil contains products hydrocarbons containing not more than 6 or 7 carbon atoms, which almost completely transforms hydrocarbons into methane and CO2 during the pre-reforming which is conducted at temperatures much lower than those used for steam reforming of methane. So, we do not form coke during this stage higher.

The HDO of the pyrolysis oil can be made at a temperature of 150 to 350 C and a pressure of 100 to 200 bar.

The HDO of the pyrolysis oil can be carried out in one or two series reactors. In the latter case, the first reactor operates at a temperature of 120 to 180 C, preferably at 150 C, the second operating at a higher temperature of 300 to 400 C, preferentially at 350 ° C.
The hydrodeoxygenation of the pyrolysis oil is carried out under a pressure of 100 to 200 bar. The use of high pressures makes it possible to promote the reaction of HDO and to avoid as much as possible the formation of coke on the hydrotreatment catalysts as well as decrease the speed of the polymerization reactions of pyrolysis compared to HDO reactions.

The pre-reforming can be carried out at a temperature of 225 to 450 C, under a pressure of 1 to 30 bar (the use of pressures is not favorable from a thermodynamic point of view but reduces the volume of reactors and thus limits the investment costs). The temperature range considered allows to place oneself in a favorable thermodynamic field and to avoid the reactions that lead to the formation of coke. The reactor considered can be of the fluidized bed or fixed bed type, preferably of fixed bed type.

Pre-reforming will preferably be done with a ratio molar water / HC load high, 10 to 15. This ratio is higher than what the thermodynamics of the reaction requires (about 3 to 4). From this fact, it allows both to shift the equilibrium of the reaction towards the

10 production of methane and hydrogen and also to limit the coke formation. So, depending on the water / organic ratio of the light aqueous fraction arriving in charge of the pre-reformer, water will be added in order to obtain an oxygen / water ratio that will be preferentially close to 13.
The steam reforming (unit SMR 28) can be carried out at a temperature of 600-900 C under a pressure of 1 to 30 bar (the use of high pressures is generally not favorable to a thermodynamic point of view but makes it possible to reduce the volume of reactors and thus to limit investment costs). The steam reforming will preferably be performed with a molar ratio water / HC load from 3 to 4. Typically, steam reforming can be made in many small tubes (several hundred) filled with catalysts.
It may also provide a catalytic conversion step residual CO, possibly followed by a purification step of hydrogen, after the effluent treatment step in the SMR unit.
The step of catalytic conversion of the residual CO is obtained by displacement (Water Gas Shift) of the following equilibrium in favor of C02 formation:
CO + H2O = CO2 + H2.
This displacement is favored at low temperature and with a ratio water / C high.
The purification of hydrogen is for example carried out by the PSA (English Pressure Swing Absorber) process based on the absorption of impurities on molecular sieves.

11 The invention is now described with reference to the accompanying drawing and non-limiting examples.
The single figure shows a diagram of an installation allowing the implementation of the method according to the invention.
The installation includes a hydrodeoxygenation unit (HDO) 10. This unit HDO 10 is fed in charge to treat 12, the oil of pyrolysis, and in hydrogen 14.
The effluent 16 leaving the HDO unit 10 is separated into one light aqueous fraction 18 and a heavy organic fraction 20.
The light aqueous fraction 18 is then fed into a pre-reformer 22 which is supplied with water vapor 24.
The effluent 26 leaving the pre-reformer 22 is then sent in a SMR unit 28 to produce hydrogen.
The residual CO contained in hydrogen can be converted into a unit 30 water gas shift and then the purified hydrogen in a unit PSA 32, to obtain purified hydrogen 34.
The heavy organic fraction is sent in charge of a hydrotreatment unit (HDT) 40.
It can be expected to split this heavy organic fraction before it was sent to HDT 40, one of the cuts obtained by example the diesel cut, being returned to the HDT.
This unit HDT 40 is supplied with H2 42 and possibly in diesel type charge 44 which may be derived from a distillation of a crude oil (Gasoil straight run), a distillation under vacuum of the atmospheric residue (vacuum gas oil) or a charge of diesel type resulting from a conversion process. The effluent 46 obtained in HDT 40 can be used as fuel bases of the LPG type liquefied petroleum), gasoline, kerosene, diesel, vacuum gas oil ...
The effluent 46 can also be in the form of two phases of which a light aqueous fraction 48 and an organic fraction 50. The light aqueous fraction 48 can then be sent to pre-reformer load 22 as required. The organic fraction Heavy 50 is used for fuel.

The hydrogen obtained 34 can then be used in a refinery, but will preferably be used to power the HDO unit 10 and / or the unit HDT 40.

12 The method according to the invention thus has the advantage of being able to be implemented in an existing installation in which only one an HDO unit and a pre-reformer will have been added. The units 26 (SMR), 28 and 30 (PSA) can indeed be part of an installation existing H2 production, while the HDT unit is part of a classic refinery scheme.

Example An installation as described with reference to the unique figure. The HDO unit 10, the pre-reformer 22 and the SMR unit 28 operate under the following conditions HDO:
Temperature: 150-350 C
Pressure: 150 Bars Pre-reformer:
Inlet temperature: 250-450 C
Pressure: 30 bars GHSV: 1000 h-1 S / C (molar): 13 Vapororeforming:
Inlet temperature in the tube: 580-620 C
Temperature Output in the tube: 850-870 C
Pressure: 30 bars S / C (molar): 3 to 4 The characteristics of the pyrolysis oil used are presented in Table 3 below.

13 Table 3 Pyrolysis oil ex-wood (coniferous) Water content (% m / m) 21.7 Solids content (% m / m) 0.17 Kinematic viscosity at 50 C (cst) 17.1 Ash content (% m / m) 0.015 Carbon Conradson (% m / m) 19.9 Density (kg / m3) 1227 PCS (MJ / kg) 18.2 Carbon content (% m / m) 46.1 Hydrogen content (% m / m) 7.4 Oxygen content (% m / m) 46.5 The flow rate of the input pyrolysis oil charge is 307kT / year. With this wood type biomass pyrolysis oil, containing 25% (mass) of water and 75% (mass) of organic compounds and under these conditions, the mass flow rates observed as a fraction organic and aqueous fraction at the output of the HDO are as follows:
138 kT / yr of heavy organic fraction, a yield mass of about 45%.
169 kT / yr of light aqueous fraction, a yield about 55%.

The composition of the light aqueous fraction is about 50%
water and about 50% organic products, while composition of the heavy organic fraction is about 1% water and 99% of organic products (% by weight).

The effluent leaving the HDT results in 115 kT / year of bases fuel, 83.3% in mass yield, and 23 kT / yr slight aqueous fraction, ie 16.7% in mass yield.

The mass yield of hydrogen leaving the PSA unit by The mass of treated pyrolysis oil is about 16%. This hydrogen is therefore resulting from the treatment by pre-reforming a load of 192 kT / year a light aqueous fraction obtained by the two stages

14 hydrodeoxygenation and hydrotreating. The consumption with HDO and HDT being about 5% by weight mass of charge entering HDO + HDT, the process implemented according to the invention is self-sufficient in hydrogen, and therefore does not require no external supply of hydrogen.

Claims (10)

1. A method of upgrading pyrolysis oil comprising the following steps :
.cndot. pre-reforming a light aqueous fraction, obtained after a treatment of hydrodeoxygenation of the oil of pyrolysis, followed by separation of an effluent obtained in said light aqueous fraction and a heavy organic fraction, in which the hydrodeoxygenation of the pyrolysis oil is carried out in two reactors in series, the first operating at a temperature of 120 to 180 ° C, and the second operating at a higher temperature of 300 to 400 ° C;
in which the pre-reforming is carried out at a temperature of 225 to 450 ° C under a pressure of 1 to 30 bar;
.cndot. treating said pre-reformed aqueous fraction in a SMR unit to produce hydrogen; and .cndot. hydrotreatment or catalytic cracking or visbreaking heavy organic fraction. 2. The recovery process according to claim 1, in which which hydrogen (34) produced from the light aqueous fraction (18) is used for the hydrotreatment (40) or catalytic cracking of the heavy organic fraction (20) or for the hydrodeoxygenation (10) of the pyrolysis oil (12). 3. The recovery process according to one of claims 1 or 2, wherein the effluent (46) obtained during the hydrotreatment (40) of the heavy organic fraction (20) is separated into a second fraction light aqueous solution (48) and a heavy organic fraction (50) when the amount of aqueous fraction is large enough to can be separated, the second light aqueous fraction (48) being sent to pre-reforming (22) with the light aqueous fraction (18) from the hydrodeoxygenation (10) of the pyrolysis oil. 4. The recovery process according to one of claims 1 to 3, wherein the heavy organic phase (20) derived from the hydrodeoxygenation (10) of the pyrolysis oil is fractionated before the hydrotreating step (40). 5. The recovery process according to one of claims 1 to 4, in which, during the hydrotreating step, the organic phase heavy (20) resulting from the hydrodeoxygenation (10) of the pyrolysis oil, or a diesel cut from the fractionation of the organic phase heavy (20) resulting from the hydrodeoxygenation (10) of the pyrolysis oil, is co-treated with a diesel type charge (44), resulting from a atmospheric distillation of crude oil, distillation under vacuum of the atmospheric residue or a diesel-type charge from a conversion process. 6. The recovery process according to one of claims 1 to 5, wherein the second light aqueous phase (18) derived from the hydrodeoxygenation (10) of the pyrolysis oil contains products hydrocarbons containing not more than 6 or 7 carbon atoms. 7. The recovery process according to one of claims 1 to 6, in which the hydrodeoxygenation of the pyrolysis oil is carried out at a pressure of 100 to 200 bar. 8. The recovery process according to one of the claims there 7, in which the pre-reforming is carried out with a molar ratio water / HC load from 10 to 15. The process according to one of claims 1 to 8, wherein a step of catalytic conversion of the residual CO is carried out after the effluent treatment step (26) in the SMR unit (28). The method of claim 9, wherein the step of Catalytic conversion of residual CO is followed by a step of purification of hydrogen.